So far as I know, the oldest in the English language at least, is Banting's Letter on Corpulence. Having lost weight and dramatically improved his health on a low carbohydrate diet. Banting wrote and self-published the book back in the Mid-Victorian era, and he distributed it for free.
Read More »Berryblast Spry Xylitol-Sweetened Mints 45-Piece Tube by Xlear
Berryblast Spry Xylitol-Sweetened Mints 45-Piece Tube by Xlear
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